Such a lighting device is disclosed in DE 10 2010 028 949 A1, for example. Said document describes a lighting device including a laser light source for generating blue light and at least one pivotable mirror and also at least one light wavelength conversion element. The blue light generated by the laser light source arrangement is directed onto the surface of the light wavelength conversion element with the aid of the pivotable mirror in order to generate white light which is a mixture of yellow light converted by means of the light wavelength conversion elements and non-converted blue light.
FIG. 4 schematically illustrates such a conventional lighting device. The light which is generated by the laser light source 41 and collimated by a collimator lens (not depicted) is focused via the optical unit 42 and the pivotable mirror 43 onto the surface of the light wavelength conversion element 44. The mirror 43 is pivotable about two orthogonal pivoting axes which lie in the reflection surface of the mirror 43 and intersect at the area centroid of the reflection surface of the mirror 43. The laser light beam impinges on the reflection surface of the mirror 43 in the region of the area centroid and is deflected in the direction of the light wavelength conversion element 44. The optical unit 42, the pivotable mirror 43 and the light wavelength conversion element 44 are arranged and aligned in such a way that the laser light beam in the case of a non-deflected mirror 43, that is to say in the case of a pivoting angle of zero degrees, corresponding to the rest position of the mirror 43, is concentrated onto the surface of the light wavelength conversion element 44 centrally and with a minimal laser spot diameter. The focal point of the optical unit 42 lies on the surface of the light wavelength conversion element 44 after imaging by the mirror 43 in the case of a pivoting angle of zero degrees. FIG. 4 illustrates this state of the mirror 43 with the aid of solid lines. Moreover, with the aid of dashed lines, FIG. 4 schematically illustrates a second pivoting state of the mirror 43, which corresponds to the deflection of the mirror 43 from its rest position by an angle of greater than zero degrees. As a result of the deflection of the mirror 43 from its rest position, the focal point of the optical unit 42 migrates after imaging by the mirror 43 along the surface 45 of a sphere whose midpoint lies at the intersection point of the two pivoting axes of the mirror 43, such that the optical path for the laser light beam generated by the laser light source arrangement 41 and directed onto the light wavelength conversion element 44 by optical unit 42 and mirror 43 is lengthened. As a result, the laser light beam after deflection by the mirror 43 arranged in the pivoting position deviating from the rest position, upon impinging on the surface of the light wavelength conversion element 44, has a larger laser spot diameter than the laser light beam after deflection by the mirror 43 arranged in its rest position. The conventional lighting device therefore has the disadvantage that the diameter of the laser spot of the laser light beam impinging on the surface of the light wavelength conversion element depends on the pivoting angle of the pivotable mirror.